Carbon　dioxide　emissions　of　＂Belt　and　Road　Initiative＂　countries　account　for　one-third　of　the　global　value.　China＇s　direct　investment　in　＂Belt　and　Road　Initiative＂　countries　has　a　significant　impact　on　their　carbon　dioxide　emissions.　This　paper　studies　the　effect　of　China＇s　direct　investment　on　carbon　dioxide　emissions　in　＂Belt　and　Road　Initiative＂　countries　from　2003　to　2017.　We　apply　a　panel　quantile　model　and　the　MCMC　optimisation　method　to　estimate　the　parameters.　Then,　67　＂Belt　and　Road　Initiative＂　countries　are　divided　into　two　groups　to　compare　the　different　impacts　of　China＇s　direct　investment　on　their　carbon　dioxide　emissions.　The　empirical　results　show　that　China＇s　direct　investment　has　a　negative　impact　on　the　carbon　dioxide　emissions　of　＂Belt　and　Road　Initiative＂　countries　no　matter　the　sample　is　grouped　or　not.　In　the　group　of　high-income　countries,　every　1%　increase　in　Chinese　investment　reduces　their　carbon　dioxide　emissions　by　0.04%.　In　the　low-income　group,　for　every　1%　increase　in　China＇s　direct　investment,　the　national　carbon　dioxide　emissions　are　reduced　by　0.02%.　Thus,　it　is　suggested　that　China　should　further　strengthen　investment　cooperation　with　＂Belt　and　Road　Initiative＂　countries　in　the　future　to　promote　global　carbon　dioxide　emission　reduction.